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23 Jul 2012

Volume 101, Issue 4, Articles (04xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 101, 043101 (2012); http://dx.doi.org/10.1063/1.4737152 (4 pages)

Toshiaki Tanigaki, Yoshikatsu Inada, Shinji Aizawa, Takahiro Suzuki, Hyun Soon Park, Tsuyoshi Matsuda, Akira Taniyama, Daisuke Shindo, and Akira Tonomura
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Quenched ultraviolet defect emission and excellent scintillation performance on a photodiode from heavily cerium doped yttrium aluminum garnet

Drew T. Haven, Denys Solodovnikov, Marc H. Weber, and Kelvin G. Lynn

Appl. Phys. Lett. 101, 041101 (2012); http://dx.doi.org/10.1063/1.4738788 (4 pages)

Online Publication Date: 23 July 2012

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Single crystal cerium doped yttrium aluminum garnet boules (Ce:YAG, 0.25-4.0 at. % Ce) were grown under similar conditions by the Czochralski method. Scintillation, photoluminescence, and lifetime measurements demonstrate reduced UV defect emission and increased visible emission as cerium doping increases, resulting from greater competitiveness of cerium luminescence centers among defect centers. Photodiode energy resolutions improved significantly, where 2.0 at. % Ce:YAG displayed 8.9% (6.14% with noise reduction) at 662 keV without post-processing. Therefore large, highly doped, as grown Ce:YAG, can achieve resolutions on cost effective photodiodes that are generally observed only with photo multiplier tubes and avalanche photodiodes at low doping levels.
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78.55.Hx Other solid inorganic materials
81.10.Fq Growth from melts; zone melting and refining
85.60.Dw Photodiodes; phototransistors; photoresistors
78.70.Ps Scintillation

Efficient directional beaming from small apertures using surface-plasmon diffraction gratings

Youngkyu Lee, Kazunori Hoshino, Andrea Alù, and Xiaojing Zhang

Appl. Phys. Lett. 101, 041102 (2012); http://dx.doi.org/10.1063/1.4738890 (4 pages) | Cited 2 times

Online Publication Date: 23 July 2012

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We demonstrate efficient optical directional beaming using an array of sub-wavelength patterns on a metallic surface. Specifically, a sub-wavelength sized slit placed next to a periodic grating is designed and optimized to realize maximum coupling efficiency and directional radiation into a leaky-wave plasmonic mode. Collective scattering from the corrugations forming the grating is synthesized to radiate towards the desired direction, and efficient beaming is achieved through tailoring the design parameters with a simple analytical model. We also prove that directivity can be further enhanced by improving the slit-grating coupling efficiency through efficient plasmon generation, showing improved angular response in far-field radiation.
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42.79.Dj Gratings

Electrical effects of metal nanoparticles embedded in ultra-thin colloidal quantum dot films

F. J. Beck, F. P. Garcia de Arquer, M. Bernechea, and G. Konstantatos

Appl. Phys. Lett. 101, 041103 (2012); http://dx.doi.org/10.1063/1.4738993 (5 pages) | Cited 1 time

Online Publication Date: 23 July 2012

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Plasmonic light trapping can increase the absorption of light in thin semiconductor films. We investigate the effect of embedded metal nanoparticle (MNP) arrays on the electrical characteristics of ultra-thin PbS colloidal quantum dot (CQD) photoconductors. We demonstrate that direct contact with the metal nanoparticles can suppress or enhance the photocurrent depending on the work function of the metal, which dominates the optical effects of the particles for ultra-thin films. These results have implications for designing plasmonic CQD optoelectronic devices.
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73.21.La Quantum dots
73.22.Lp Collective excitations
78.67.Hc Quantum dots
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Liquid-based infrared optical switch

Hongwen Ren, Su Xu, Yifan Liu, and Shin-Tson Wu

Appl. Phys. Lett. 101, 041104 (2012); http://dx.doi.org/10.1063/1.4738995 (5 pages) | Cited 2 times

Online Publication Date: 23 July 2012

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multimedia

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We report an infrared (IR) optical switch using a position-shifting glycerol droplet. The droplet is surrounded by density-matched oil. In the voltage-on state, the droplet shifts in one direction. Upon removing the voltage, the droplet returns to its original position with the aid of interfacial tensions. Due to the strong absorption of glycerol at 1.55 μm, our IR optical switch shows ∼95:1 contrast ratio and ∼200 ms response time. Such a device is promising for fiber optical switch and various IR optical attenuators.
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42.79.Ta Optical computers, logic elements, interconnects, switches; neural networks

Generation of a beam of fast electrons by tightly focusing a radially polarized ultrashort laser pulse

S. Payeur, S. Fourmaux, B. E. Schmidt, J. P. MacLean, C. Tchervenkov, F. Légaré, M. Piché, and J. C. Kieffer

Appl. Phys. Lett. 101, 041105 (2012); http://dx.doi.org/10.1063/1.4738998 (3 pages) | Cited 1 time

Online Publication Date: 23 July 2012

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The generation of an electron beam through longitudinal field acceleration from a tightly focused radially polarized (TM01) laser mode is reported. The longitudinal field is generated by focusing a TM01 few-cycle laser pulse (1.8 μm, 550 μJ, 15 fs) with a high numerical aperture parabola. The created longitudinal field in the focal region is intense enough to ionize atoms and accelerate electrons to 23 keV of energy from a low density oxygen gas. The characteristics of the electron beam are presented.
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42.60.Fc Modulation, tuning, and mode locking
29.20.Ej Linear accelerators

InGaAs quantum wire intermediate band solar cell

Vas. P. Kunets, C. S. Furrow, T. Al. Morgan, Y. Hirono, M. E. Ware, V. G. Dorogan, Yu. I. Mazur, V. P. Kunets, and G. J. Salamo

Appl. Phys. Lett. 101, 041106 (2012); http://dx.doi.org/10.1063/1.4737944 (5 pages)

Online Publication Date: 23 July 2012

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Intermediate band solar cells were realized using a GaAs (311)A p-i-n junction with Si as both the p- and n-type dopant, where the intermediate band was realized with a stack of InGaAs quantum wires. This quantum wire photovoltaic device demonstrates a non-trivial increase in solar cell efficiency over a reference p-i-n GaAs (311)A junction resulting from a significant increase in short circuit current and an only slight decrease in open circuit voltage. Presented are optical and electrical characterizations of these devices.
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88.40.jm Thin film III-V and II-VI based solar cells
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
88.40.hj Efficiency and performance of solar cells

Highly efficient twisted nematic liquid crystal polarization gratings achieved by microrubbing

M. Honma and T. Nose

Appl. Phys. Lett. 101, 041107 (2012); http://dx.doi.org/10.1063/1.4737945 (4 pages) | Cited 1 time

Online Publication Date: 23 July 2012

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We demonstrate twisted nematic liquid crystal (LC) polarization gratings (TNPGs) with a high first-order diffraction efficiency (>90%) that have the twist angle as constant, whereas the azimuthal angle of the mid-plane liquid-crystal director varies linearly in space. The high diffraction-efficiency design scheme is derived by means of the Jones matrix method. The designed first-order diffraction efficiency theoretically reaches 100% for the thick LC layer in which the retardation equals (n + 1/2)λ (n is an integer and λ is the wavelength). We also present a simple model for the grating period- and twist angle-dependent threshold voltage of the Freedericksz transition in TNPGs.
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42.70.Df Liquid crystals
42.79.Dj Gratings
42.82.Cr Fabrication techniques; lithography, pattern transfer

Continuous-wave operation and differential gain of InGaN/GaN quantum dot ridge waveguide lasers (λ = 420 nm) on c-plane GaN substrate

Animesh Banerjee, Thomas Frost, Ethan Stark, and Pallab Bhattacharya

Appl. Phys. Lett. 101, 041108 (2012); http://dx.doi.org/10.1063/1.4738499 (4 pages) | Cited 1 time

Online Publication Date: 23 July 2012

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The differential gain and coherent output characteristics of blue-emitting In0.18Ga0.82N/GaN quantum dot ridge waveguide lasers have been measured. The laser heterostructures were grown by molecular beam epitaxy. Injected carrier lifetimes in the quantum dots have been measured by temperature dependent and time resolved photoluminescence measurements. The radiative lifetime at 280 K is 480 ps. The threshold current densities at room temperature are 930 and 970 A/cm2 for pulsed and continuous wave bias operation, respectively. The measured differential gain is 2 × 10−16 cm2. The output slope and wall plug efficiency at 1050 A/cm2 under continuous wave operation are 0.4 W/A and 0.4%, respectively. The measured blue shift in the emission wavelength due to screening of the piezoelectric field with injection is as small as 4.4 nm.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems

Coupling into tapered metal parallel plate waveguides using a focused terahertz beam

M. Gerhard, M. Theuer, and R. Beigang

Appl. Phys. Lett. 101, 041109 (2012); http://dx.doi.org/10.1063/1.4738982 (4 pages)

Online Publication Date: 24 July 2012

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Coupling of focused terahertz radiation into tapered metal parallel plate waveguides with sub-wavelength gap widths is presented. A line-focus terahertz time-domain spectroscopy setup with flexible foci is used to investigate coupling of broadband terahertz radiation from free-space into waveguides for different gap widths. Various waveguide lengths are compared in experiment and calculation in terms of occurring loss and divergence phenomena. Amplitude coupling ratios of 80% from free-space into the waveguides are obtained.
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84.40.Az Waveguides, transmission lines, striplines

Ultraviolet electroluminescence from horizontal ZnO microrods/GaN heterojunction light-emitting diode array

G. Y. Zhu, C. X. Xu, Y. Lin, Z. L. Shi, J. T. Li, T. Ding, Z. S. Tian, and G. F. Chen

Appl. Phys. Lett. 101, 041110 (2012); http://dx.doi.org/10.1063/1.4739002 (4 pages) | Cited 2 times

Online Publication Date: 24 July 2012

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ZnO microrods were assembled on p-GaN substrate to form a heterostructural light-emitting diode (LED) array. Ultraviolet (UV) emission was obtained under a low forward bias of 3.5 V. The investigation on the electroluminescence, photoluminescence demonstrated three distinct electron-hole recombination processes. The relative intensity of these three emission bands changed with increase of the forward bias, and resulted in blue shift and spectral narrowing of electroluminescence. The present work provides a facile technique for micro-/nano-devices fabrication besides obtaining UV LED arrays.
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85.60.Jb Light-emitting devices

Light sailboats: Laser driven autonomous microrobots

Anrdás Búzás, Lóránd Kelemen, Anna Mathesz, László Oroszi, Gaszton Vizsnyiczai, Tamás Vicsek, and Pál Ormos

Appl. Phys. Lett. 101, 041111 (2012); http://dx.doi.org/10.1063/1.4737646 (5 pages) | Cited 1 time

Online Publication Date: 24 July 2012

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We introduce a system of light driven microscopic autonomous moving particles that move on a flat surface. The design is simple, yet effective: Micrometer sized objects with wedge shape are produced by photopolymerization, and they are covered with a reflective surface. When the area of motion is illuminated perpendicularly from above, the light is deflected to the side by the wedge shaped objects, in the direction determined by the position and orientation of the particles. The momentum change during reflection provides the driving force for an effectively autonomous motion. The system is an efficient tool to study self propelled microscopic robots.
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07.07.Tw Servo and control equipment; robots
42.62.-b Laser applications
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
89.40.Cc Water transportation

Ultrafast third order nonlinear optical response of donor and acceptor codoped and compensated silicon quantum dots

Kenji Imakita, Masahiko Ito, Ryo Naruiwa, Minoru Fujii, and Shinji Hayashi

Appl. Phys. Lett. 101, 041112 (2012); http://dx.doi.org/10.1063/1.4739237 (4 pages) | Cited 2 times

Online Publication Date: 24 July 2012

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Nonlinear optical responses of phosphorus and boron codoped and compensated silicon quantum dots (Si-QDs) embedded in borophosphosilicate glass were studied by a z-scan and an optical Kerr gate methods under femtosecond excitation at 780 nm. The nonlinear refractive index (n2) and the two photon absorption coefficients (β) of compensated Si-QDs were found to be enhanced several times compared to those of intrinsic Si-QDs. The response time was shorter than our time resolution of 100 fs at room temperature.
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78.67.Hc Quantum dots
78.47.J- Ultrafast spectroscopy (<1 psec)
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

High thermal performance of μ-stripes quantum cascade laser

G. M. de Naurois, B. Simozrag, G. Maisons, V. Trinité, F. Alexandre, and M. Carras

Appl. Phys. Lett. 101, 041113 (2012); http://dx.doi.org/10.1063/1.4739004 (4 pages)

Online Publication Date: 25 July 2012

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We demonstrate high thermal dissipation of quantum cascade lasers (QCLs) using multi-stripes array technology. Buried QCL arrays offer both lateral dissipation enhancements while keeping beam quality control for large active region lasers. Experimental thermal resistances down to 2 K/W are reported. InP:Fe regrowth morphology has been optimized to limit current leakage. Thermal resistance decreasing with both number and width of emitters is demonstrated. Comparison with simulation shows excellent agreement, with a reduction factor of 3 when comparing to standard ridges QCL. These low thermal resistances project up to 40 W in continuous wave operation using state-of-the-art QCL design.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems

Suppression of cross-hatched polariton disorder in GaAs/AlAs microcavities by strain compensation

Joanna M. Zajac, Edmund Clarke, and Wolfgang Langbein

Appl. Phys. Lett. 101, 041114 (2012); http://dx.doi.org/10.1063/1.4739245 (4 pages) | Cited 1 time

Online Publication Date: 25 July 2012

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Zinc-blende semiconductor heterostructures grown in the [001] direction with a small lattice mismatch accommodate stress by developing a cross-hatch dislocation pattern. In GaAs based planar microcavities grown by molecular beam epitaxy, this pattern creates a potential landscape for exciton-polaritons, causing scattering and localization. We report here on suppressing the cross-hatch by introducing strain-compensating AlP layers into the center of the low index AlAs layers of the distributed Bragg reflectors. We observe a reduction of the cross-hatch dislocation density by at least one order of magnitude for 1.1 nm thick AlP layers, which correspond to an effective AlAs0.985P0.015 low index layer. These compensated structures show a remaining polariton disorder potential in the 10 μeV range.
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42.79.Bh Lenses, prisms and mirrors

Improved quantum efficiency in InGaN light emitting diodes with multi-double-heterostructure active regions

X. Li, S. Okur, F. Zhang, S. A. Hafiz, V. Avrutin, Ü. Özgür, H. Morkoç, and K. Jarašiūnas

Appl. Phys. Lett. 101, 041115 (2012); http://dx.doi.org/10.1063/1.4739419 (4 pages) | Cited 1 time

Online Publication Date: 25 July 2012

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InGaN light emitting diodes (LEDs) with multiple thin double-heterostrucutre (DH) active regions separated by thin and low energy barriers were investigated to shed light on processes affecting the quantum efficiency and means to improve it. With increasing number of 3 nm-thick DH active layers up to four, the electroluminescence efficiency scaled nearly linearly with the active region thickness owing to reduced carrier overflow with increasing total thickness, showing almost no discernible efficiency degradation at high injection levels up to the measured current density of 500 A/cm2. Comparison of the resonant excitation dependent photoluminescence measurements at 10 K and room temperature also confirmed that further increasing the number of DH layers beyond six results in degradation of the material quality, and therefore, increasing nonradiative recombination. Using multiple DH active regions is shown to be a superior approach for quantum efficiency enhancement compared with simply increasing the single DH thickness or the number of quantum wells in LED structures due to better material quality and larger number of states available.
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85.60.Jb Light-emitting devices
78.55.Cr III-V semiconductors
78.60.Fi Electroluminescence

Emission enhancement in GaN-based light emitting diodes with shallow triangular quantum wells

Shanjin Huang, Zimin Chen, Yulun Xian, Bingfeng Fan, Zhiyuan Zheng, Zhisheng Wu, Hao Jiang, and Gang Wang

Appl. Phys. Lett. 101, 041116 (2012); http://dx.doi.org/10.1063/1.4739445 (4 pages) | Cited 2 times

Online Publication Date: 25 July 2012

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GaN-based light emitting diodes (LEDs) with shallow triangular quantum wells (TQW) structure were proposed and investigated. LEDs with shallow TQW demonstrated a lower turn-on voltage and 80% higher lighting efficiency at 20 mA than devices without the shallow QW structure. A more stable emission wavelength and a lower ideality factor were achieved with the proposed structure. X-ray reciprocal space mapping revealed a partial strain relaxation in active region due to the insertion of the TQW structure. The improved performance is ascribed to the weakening of the polarization field in the MQW active region induced by the TQW structure.
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85.60.Jb Light-emitting devices

Demonstration of low-loss on-chip integrated plasmonic waveguide based on simple fabrication steps on silicon-on-insulator platform

Landobasa Y. M. Tobing, Liliana Tjahjana, and Dao Hua Zhang

Appl. Phys. Lett. 101, 041117 (2012); http://dx.doi.org/10.1063/1.4739523 (4 pages)

Online Publication Date: 25 July 2012

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We report the experimental realization of a robust silicon-based plasmonic waveguide structure which can theoretically provide sub-wavelength confinement for Ex- and Ey-polarized surface plasmon polariton modes. Our waveguides exhibit propagation loss as low as 0.2 dB/μm with ∼50% coupling efficiency.
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42.82.Et Waveguides, couplers, and arrays
42.79.Gn Optical waveguides and couplers
42.82.Cr Fabrication techniques; lithography, pattern transfer

10 GHz fundamental mode fiber laser using a graphene saturable absorber

Amos Martinez and Shinji Yamashita

Appl. Phys. Lett. 101, 041118 (2012); http://dx.doi.org/10.1063/1.4739512 (3 pages) | Cited 1 time

Online Publication Date: 26 July 2012

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All-fiber mode-locked lasers with fundamental repetition rates of several gigahertz are sought after for applications in optical communications and metrology. In this paper, we propose a fiber Fabry-Pérot laser mode-locked by a graphene-based saturable absorber that operates at a fundamental repetition rate of 9.67 GHz. We use this laser as the seed for the generation of supercontinuum with 0.08 nm mode spacing.
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42.55.Wd Fiber lasers
42.60.By Design of specific laser systems
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.60.Fc Modulation, tuning, and mode locking
42.65.-k Nonlinear optics
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Towards secondary ion mass spectrometry on the helium ion microscope: An experimental and simulation based feasibility study with He+ and Ne+ bombardment

T. Wirtz, N. Vanhove, L. Pillatsch, D. Dowsett, S. Sijbrandij, and J. Notte

Appl. Phys. Lett. 101, 041601 (2012); http://dx.doi.org/10.1063/1.4739240 (5 pages) | Cited 1 time

Online Publication Date: 25 July 2012

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The combination of the high-brightness He+/Ne+ atomic level ion source with secondary ion mass spectrometry detection capabilities opens up the prospect of obtaining chemical information with high lateral resolution and high sensitivity on the Zeiss ORION helium ion microscope. The analytical performance in terms of sputtering yield, useful yield, and detection limit is studied and subsequently optimized by oxygen and cesium flooding. Detection limits down to 10−6 and 10−5 can be obtained for silicon using Ne+ and He+, respectively. A simulation based study reveals furthermore that a lateral resolution <10 nm can be obtained.
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07.78.+s Electron, positron, and ion microscopes; electron diffractometers
07.75.+h Mass spectrometers

Surface modification by nonthermal plasma induced by using magnetic-field-assisted gliding arc discharge

Zongbao Feng, Noboru Saeki, Tomoyuki Kuroki, Mitsuru Tahara, and Masaaki Okubo

Appl. Phys. Lett. 101, 041602 (2012); http://dx.doi.org/10.1063/1.4738766 (4 pages)

Online Publication Date: 26 July 2012

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The authors report on the introduction of a magnetic field to gliding arc discharge (GD) in order to enhance surface modification by nonthermal plasma at atmospheric-pressure. The GD is induced between two wire electrodes by using a pulse high-voltage power supply with peak-to-peak voltage of 5 kV. When a magnetic field of 0.25 T is applied, the GD enlarged and a 19-cm-long stretch of plasma is excited. The surface treatment of polyethylene terephthalate and polytetrafluoroethylene films is performed. The adhesion improved by up to ∼30 times due to the enhanced chemical activity in the films.
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81.65.-b Surface treatments
52.77.-j Plasma applications
52.80.Mg Arcs; sparks; lightning; atmospheric electricity
68.35.Np Adhesion

Activation mechanism of carbon monoxide on α-Fe2O3 (0001) surface studied by using first principle calculations

Jianping Xiao and Thomas Frauenheim

Appl. Phys. Lett. 101, 041603 (2012); http://dx.doi.org/10.1063/1.4739935 (3 pages)

Online Publication Date: 27 July 2012

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We have employed first principle methods to investigate carbon monoxide (CO) adsorption on oxygen terminated α-Fe2O3 (0001) surface. We have found that the CO can be adsorbed and oxidized as long as the CO surface coverage reaches up to two thirds monolayer. Simultaneously, the bent CO2 are activated and dimerized. Furthermore, oxygen vacancy can dissociate water and produce carboxylic group by means of reactions with the activated CO2 dimer. Our calculations have reproduced experimental in situ observations of nanocrystalline α-Fe2O3. In this letter, we also propose a significant strategy to improve reactivity of α-Fe2O3 (0001) continuous film, to convert more efficiently CO into organic species.
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68.43.Mn Adsorption kinetics
61.72.jd Vacancies

Cathode-like luminescence from vacuum-dielectric interface induced by self-stabilizing secondary electron emission

Jiang-Yang Zhan (詹江杨), Hai-Bao Mu (穆海宝), Guan-Jun Zhang (张冠军), Xue-Zeng Huang (黄学增), Xian-Jun Shao (邵先军), and Jun-Bo Deng (邓军波)

Appl. Phys. Lett. 101, 041604 (2012); http://dx.doi.org/10.1063/1.4738999 (4 pages) | Cited 1 time

Online Publication Date: 27 July 2012

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A kind of interesting luminescence phenomenon from vacuum-dielectric interface under high electric field is presented in this Letter. It is visible, steady, and continuous, occurring before or accompanied with flashover across dielectric, which is quite different from general electroluminescence from insulator surface reported before. By investigating its optical and electrical characteristics, we consider it as cathode-like luminescence, which is initialized by the field electron emission from cathode triple junction and finally generated by the process of radiative recombination due to the self-stabilizing secondary electron emission and collision on insulator surface.
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78.60.Hk Cathodoluminescence, ionoluminescence
79.20.Hx Electron impact: secondary emission
79.70.+q Field emission, ionization, evaporation, and desorption

Precise control of epitaxy of graphene by microfabricating SiC substrate

H. Fukidome, Y. Kawai, F. Fromm, M. Kotsugi, H. Handa, T. Ide, T. Ohkouchi, H. Miyashita, Y. Enta, T. Kinoshita, Th. Seyller, and M. Suemitsu

Appl. Phys. Lett. 101, 041605 (2012); http://dx.doi.org/10.1063/1.4740271 (4 pages)

Online Publication Date: 27 July 2012

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Epitaxial graphene (EG) on SiC is promising owing to a capability to produce high-quality film on a wafer scale. One of the remaining issues is microscopic thickness variation of EG near surface steps, which induces variations in its electronic properties and device characteristics. We demonstrate here that the variations of layer thickness and electronic properties are minimized by using microfabricated SiC substrates which spatially confines the epitaxy. This technique will contribute to the realization of highly reliable graphene devices.
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81.05.ue Graphene
81.05.Hd Other semiconductors
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
73.22.Pr Electronic structure of graphene
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Nanometer-scale tunnel formation in metallic glass by helium ion irradiation

Lin Shao, Brian P. Gorman, Assel Aitkaliyeva, N. David Theodore, and Guoqiang Xie

Appl. Phys. Lett. 101, 041901 (2012); http://dx.doi.org/10.1063/1.4734399 (4 pages)

Online Publication Date: 23 July 2012

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We have shown that upon high fluence helium ion irradiation, metallic glass Cu50Zr45Ti5 becomes highly porous at the depth of the helium projected range. The resulting porous region is characterized by the formation of a tunnel like structure and self-linkage of nanometer size gas bubbles. Furthermore, the irradiation leads to the formation of nanometer size CuxZry crystals that are randomly distributed. The results of this study indicate that the He-filled bubbles have attractive interactions and experience considerable mobility. Movement of the bubbles is believed to be assisted by ballistic collisions.
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61.82.Bg Metals and alloys
61.43.Fs Glasses

Ultrafast photoinduced mechanical strain in epitaxial BiFeO3 thin films

L. Y. Chen, J. C. Yang, C. W. Luo, C. W. Laing, K. H. Wu, J.-Y. Lin, T. M. Uen, J. Y. Juang, Y. H. Chu, and T. Kobayashi

Appl. Phys. Lett. 101, 041902 (2012); http://dx.doi.org/10.1063/1.4734512 (4 pages) | Cited 1 time

Online Publication Date: 23 July 2012

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We studied ultrafast dynamics and photoinduced mechanical strain of BiFeO3 thin films by dual-color transient reflectivity measurements (ΔR/R). Anisotropic photostriction in BiFeO3 is found to be mainly driven by the optical rectification effect. Results of the photostriction at various thicknesses show that the estimated sound velocity along [110] direction of BiFeO3 is 4.76 km/s.
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68.60.Bs Mechanical and acoustical properties
78.20.Pa Photoacoustic effects
78.47.jg Time resolved reflection spectroscopy
62.65.+k Acoustical properties of solids
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